Symptoms
- A relaying error message (550) is returned by the mail client when sending an external email message.
- An error is returned when trying to send an email message from a WebMail client.
Resolution
If you are running IIS, please ensure that the IIS SMTP service is not running. (Note, the SMTP service is installed with IIS by default on some versions of Windows.)
Using the Add/Remove Programs applet in Control Panel, select Add/Remove Windows components. Then select the Internet Information Server (IIS) component and click the Details button. Uncheck the option for the SMTP service.
Alternatively you can stop and disable this service by using the Services Applet in Control Panel. On Windows 2003 server it will also be necessary to disable the Windows POP3 service.